MN ELECTRICAL FREQUENCY AS'ALYZER 311 



table top"), air motor, etc., is also clearly shown in this figure. I-'ach 

 air relay is cquippc<l with two rubber tubes leading to adjustable, 

 cocks on the header which in turn are connected to the tracker bar. 

 The three-control relays are also shown in Fig. 6. The vacuum 

 pump is shown at v in Fig. 7. The piano roll E moves over the 

 tracker bar w and is reversed by means of solenoid Q. In boxes 

 / are placed the plate batteries for the amplifier-rectifier. 



The control apparatus by means of which the analyzer becomes 

 practically an automatic machine will now be described. Referring 

 again to Fig. 3 it will be seen that there is provided an auxiliary 

 header and an electrically operated slide valve. The functions of 

 these devices will be discussed presently. 



The machine is started by pressing the starting button which 

 should be kept closed for a few seconds while normal vacuum is 

 being established in the headers. The air motor then starts and 

 the paper roll £ begins to tra\'el across the tracker bar. Perfora- 

 tions in the roll are so made that when the roll is in its initial position 

 an opening allows air to enter chamber N of the holding relay. As 

 soon as the paper starts, however, this opening is closed, chamber N 

 is exhausted, and contacts K close. This short-circuits the starting 

 button which the operator may now release, and the machine is in 

 full operation. It will be noted that the closing of the contacts of 

 the starting button or contacts K puts into operation motors which 

 drive the vacuum pump and the camera apparatus. Simultaneously- 

 recording meter lamp H and scale-line lamp / are lighted. The 

 latter illuminates the record through small holes in an opaque scale 

 strip thus marking horizontal lines due to the motion of the record. 



As the roll E traverses the tracker bar, appropriate perforations 

 control the condenser relays so as to switch the proper condensers 

 into and out of the tuned circuit. Proper perforations also control 

 the frequency lamp relay which flashes frequency lines on the record 

 by means of Lamp G. Relay F is inserted in order to make the 

 flash of short duration. 



The tracker bar-paper-roll apparatus was received as a unit from 

 the manufacturer and was installed after making modification in 

 the reversing mechanism as mentioned abo\-e. This was done in 

 the interest of automatic control. The paper roll is kept in its proper 

 course over the tracker bar by means of an automatic adjusting 

 device such as used in practically all high grade player pianos. 



As the paper progresses over the tracker bar a point is finally 

 reached where the last condenser connections are made and it be- 

 comes necessary to rewind the roll and to restore the entire mechanism 



